Search Results (18)

Control valves in nuclear systems operate under high-pressure differentials generating intense transient fluid forces that induce destructive structural vibrations, risking resonance and the valve stem fracture. In this study, computational fluid dynamics (CFD) was employed to characterize the internal flow dynamics of the valve, supported by experiment validation of the fluid model. To account for nonlinear structural effects such as contact and damping, a coupled fluid–structure interaction approach incorporating nonlinear perturbation analysis was applied to evaluate the dynamic response of the valve core assembly under fluid excitation. The results indicate that flow separation, re-circulation, and vortex shedding within the throttling region are primary contributors to structural vibrations. A comparative analysis of stability coefficients, modal damping ratios, and logarithmic decrements under different valve openings revealed that the valve core assembly remains relatively stable overall. However, critical stability risks were identified in the lower-order modal frequency range at 50% and 70% openings. Notably, at a 70% opening, the first-order modal frequency of the valve core assembly closely aligns with the frequency of fluid excitation, indicating a potential for critical resonance. This research provides important insights for evaluating and enhancing the vibration stability and operational safety of control valves under complex flow conditions. Full article

This article presents the instrumentation of an electronic–mechanical differential prototype, consisting of an arrangement of three throttles to operate two hub motors on the rear wheels of an electric vehicle. Each motor is connected to its respective throttle, while a third throttle is connected in series with the other two. This configuration allows for speed control during both rectilinear and curvilinear motion, following Ackermann differential geometry, in a simple manner and without the need for complex electronic systems that make the electronic differential more expensive. The differential throttles are strategically positioned on the mass bars connected to the steering system, ensuring that the rear wheels maintain the appropriate differential ratio. For this reason, it is referred to as an “electronic–mechanical differential”. Additionally, this method can be extended to a four-wheel differential system. Full article

The performances of two linear aerospike nozzles, generated by truncating the same plug contour at 40% and 20% of its ideal length, are investigated numerically within a two-dimensional approximation and compared with each other. The nozzle geometry is a 2D representation, extracted from the CAD model of the actual nozzles under experimental investigation. In the working conditions studied here, the nozzle is throttled differentially, by setting different flow conditions on the upper and lower inlet, with the aim of generating thrust vectoring effects. The performances and flowfield of both aerospikes are investigated for values of the nozzle pressure ratio (npr) ranging from 3.7 up to the design condition ($\mathrm{NPR}=200$), and for several levels of differential throttling. The CFD approach adopted is based on a two-dimensional RANS flow model. Comparisons between the numerical and experimental data are performed at two nozzle working conditions: without and with differential throttling. The numerical results are in good agreement with the experimental data. Moreover, the numerical simulations of the throttling case have shown a thrust deflection of about 5 degrees, with a differential pressure of approximately 10 percent. Full article

Intelligent pipeline inspection is necessary to operate submarine pipelines safely. At present, speed excursion and blockage are the challenges in the inspection of low-pressure gas pipelines. Accordingly, this study proposes a novel pneumo-electric hybrid-driven scheme to improve the traveling stability of inspection robots. To adapt to different working conditions, building blocks and CFD numerical simulation methods are used to study the throttling pressure control flow field of the robot. The results proved that the flow clearance had the most evident effect. The flow clearance was reduced from 30 to 5 mm, and the differential pressure of the prototype increased from 0.3 to 17 kPa. The skeleton diameter has a small effect on the differential pressure. The differential pressure increases as the gas velocity increases. By analyzing the prototype in different positions, it was found that the differential pressure of the prototype while passing the elbow decreased by 45% at 45°, which quantified the fluid-driven force gap of the prototype while passing through the elbow. Finally, by comparing the speed of prototype with that of fluid-driven pig, it is demonstrated that a pneumo-electric hybrid-driven scheme is an effective solution to the problem of unstable inspection operation of low-pressure gas pipelines. Full article

The throttling performance of conventional throttle orifice structures of fluid control valves is very low. Therefore, this paper proposes a novel trapezoidal throttle orifice with excellent throttling performance. The effect of the taper of the throttle orifice on the erosion was researched. Firstly, two schemes of trapezoidal throttle orifice were proposed according to the fluid control valve. Secondly, the excellent throttling performance of the trapezoidal throttle orifice was compared and optimized. Finally, a numerical simulation method of the erosion-resistant ability of the trapezoidal throttle orifice was established. It was found that for the same throttling area, the differential pressure of the trapezoidal orifice was higher than that of the conventional rectangular orifice by about 18.6%. The taper had little effect on the gas production, which increased by only 3.3% during the 10° to 30° change. The maximum erosion was firstly reduced and then increased with increases in the angle from 0 to 25°of the taper. Moreover, the minimum was achieved at about a 20° taper angle. The above research methods provide a theoretical basis for optimizing the size and structure of orifices and the sealing reliability of fluid control valves. Full article

Spider silk has extraordinary mechanical properties, displaying high tensile strength, elasticity, and toughness. Given the high performance of natural fibers, one of the long-term goals of the silk community is to manufacture large-scale synthetic spider silk. This process requires vast quantities of recombinant proteins for wet-spinning applications. Attempts to synthesize large amounts of native size recombinant spidroins in diverse cell types have been unsuccessful. In these studies, we design and express recombinant miniature black widow MaSp1 spidroins in bacteria that incorporate the N-terminal and C-terminal domain (NTD and CTD), along with varying numbers of codon-optimized internal block repeats. Following spidroin overexpression, we perform quantitative analysis of the bacterial proteome to identify proteins associated with spidroin synthesis. Liquid chromatography with tandem mass spectrometry (LC MS/MS) reveals a list of molecular targets that are differentially expressed after enforced mini-spidroin production. This list included proteins involved in energy management, proteostasis, translation, cell wall biosynthesis, and oxidative stress. Taken together, the purpose of this study was to identify genes within the genome of Escherichia coli for molecular targeting to overcome bottlenecks that throttle spidroin overexpression in microorganisms. Full article

Video streaming service delivery is a challenging task for mobile network operators. Knowing which services clients are using could help ensure a specific quality of service and manage the users’ experience. Additionally, mobile network operators could apply throttle, traffic prioritization, or differentiated pricing. However, due to the growth of encrypted Internet traffic, it has become difficult for network operators to recognize the type of service used by their clients. In this article, we propose and evaluate a method for recognizing video streams solely based on the shape of the bitstream on a cellular network communication channel. To classify bitstreams, we used a convolutional neural network that was trained on a dataset of download and upload bitstreams collected by the authors. We demonstrate that our proposed method achieves an accuracy of over 90% in recognizing video streams from real-world mobile network traffic data. Full article

The main valve spool structure of the pilot-operated proportional directional valve is diverse and has a direct impact on the flow field. To improve the valve’s performance, this work studied the characteristics of four types of spool structures with the following throttling groove arrangements: no throttling groove, a U-shaped groove, a triangle groove, and a combined groove. This study analyzed the flow field simulation of four spool structures under the same opening degree and different pressures to study the flow field cavitation characteristics and pressure distribution in the valve. According to the simulation results, the necessity of opening throttling grooves for the pilot proportional directional valve and the advantages of combined grooves over U-shaped and triangular grooves were verified. Then, the proportional valve with a combined groove structure was simulated and analyzed to study its throttling characteristics, steady flow characteristics, and flow and load differential pressure characteristics, and further explore the advantages of a combined groove. Finally, the experimental results are compared with the simulation results, which can provide a theoretical reference for the selection of the throttle groove of the proportional valve and the structural design of the slide valve. Full article

In response to the widespread adoption of vehicle-following systems in autonomous applications, the demand for collision warning to enable safer functionalities is increasing. This study provides an approach for automated vehicle guidance to follow the preceding vehicles longitudinally and puts emphasis on the performance of collision avoidance. The safety distance model is established, which contains a distance compensation algorithm to deal with the special case on curved roads. By introducing the algorithm of velocity and distance prediction, the collision risks are detected and measured in real time. The objective function is established based on optimal control theory to solve the desired following acceleration. The control system designed with the method of proportion integration differentiation combines throttle percentage and brake pressure as outputs to compensate acceleration. In the Carsim and Simulink co-simulation platform, the control system for longitudinal collision avoidance is simulated and analysed for four typical working conditions: the preceding vehicle drives at a constant speed on straight and curved roads, while the preceding vehicle drives at various speeds on straight and curved roads. The results validate the feasibility and effectiveness of the proposed method, which can be used for the longitudinal control of vehicle-following active collision avoidance. Full article

This paper concerns the start-up process of a hydrostatic transmission with a fixed displacement pump, with particular emphasis on dynamic surplus pressure. A numerically controlled transmission using a proportional directional valve was analysed by simulation and experimental verification. The transmission is controlled by the throttle method, and the variable resistance is the throttling gap of the proportional spool valve. A mathematical description of the gear start-up process was obtained using a lumped-parameters model based on ordinary differential equations. The proportional spool valve was described using a modified model, which significantly improved the performance of the model in the closed-loop control process. After assuming the initial conditions and parameterization of the equation coefficients, a simulation of the transition start-up was performed in the MATLAB–Simulink environment. Simulations and experimental studies were carried out for control signals of various shapes and for various feedback from the hydraulic system. The pressure at the pump discharge port and the inlet port of the hydraulic motor, as well as the rotational speed of the hydraulic motor, were analysed in detail as functions of time. In the experimental verification, complete measuring lines for pressure, speed of the hydraulic motor, flow rate, and temperature of the working liquid were used. Full article

Electro-hydraulic differential cylinder drives with variable-speed displacement units as their central transmission element are subject to an increasing focus in both industry and academia. A main reason is the potential for substantial efficiency increases due to avoidance of throttling of the main flows. Research contributions have mainly been focusing on appropriate compensation of volume asymmetry and the development of standalone self-contained and compact solutions, with all necessary functions onboard. However, as many hydraulic actuator systems encompass multiple cylinders, such approaches may not be the most feasible ones with respect to efficiency or commercial feasibility. This article presents the idea of multi-cylinder drives, characterized by electrically and hydraulically interconnected variable-speed displacement units essentially allowing for completely avoiding throttle elements, while allowing for hydraulic and electric power sharing as well as the sharing of auxiliary functions and fluid reservoir. With drive topologies taking offset in communication theory, the concept of electro-hydraulic variable-speed drive networks is introduced. Three different drive networks are designed for an example application, including component sizing and controls in order to demonstrate their potentials. It is found that such drive networks may provide simple physical designs with few building blocks and increased energy efficiencies compared to standalone drives, while exhibiting excellent dynamic properties and control performance. Full article

Measuring the viscosity and density of petroleum products is important for their proper production, transportation and application. Viscosity and density are the main parameters determining the composition and structure of petroleum products. Therefore, in the industry, to control the quality of petroleum products during various technological processes, automatic and non-automatic devices are used for their measurement. The accuracy of measuring the viscosity and density of petroleum products is an important factor. The authors analyzed different methods of measuring the viscosity and density of petroleum products and synthesized three versions of throttle bridge transducers. These versions implement differential measurement methods and have different numbers of laminar and turbulent throttles. The authors obtained new equations of static conversion functions by channels of measuring the kinematic viscosity and density of petroleum products of the proposed throttle bridge transducers. The authors developed a block diagram and designed measuring equipment to study experimentally the static characteristics of the throttle bridge transducers. The authors determined that the maximal relative deviations of the results of experimental studies from numerical calculations of a static conversion factor by channels of kinematic viscosity and density were 5.88% and 8.76%, respectively. The authors developed two versions of automatic devices for measuring the kinematic viscosity and density of petroleum products based on the proposed throttle bridge transducers. The first version is an automatic analyzer with tracking astatic balancing. The second version is an automatic analyzer with deployment balancing. The authors developed constructions of both versions of automatic analyzers and obtained the results of experimental measuring of the kinematic viscosity and density of petroleum products in different ranges. Full article

Aerospike nozzles represent an interesting solution for Single-Stage-To-Orbit or clustered launchers owing to their self-adapting capability, which can lead to better performance compared to classical nozzles. Furthermore, they can provide thrust vectoring in several ways. A simple solution consists of applying differential throttling when multiple combustion chambers are used. An alternative solution is represented by fluidic thrust vectoring, which requires the injection of a secondary flow from a slot. In this work, the flow field in a linear aerospike nozzle was investigated numerically and both differential throttling and fluidic thrust vectoring were studied. The flow field was predicted by solving the Reynolds-averaged Navier–Stokes equations. The thrust vectoring performance was evaluated in terms of side force generation and axial force reduction. The effectiveness of fluidic thrust vectoring was investigated by changing the mass flow rate of secondary flow and injection location. The results show that the response of the system can be non-monotone with respect to the mass flow rate of the secondary injection. In contrast, differential throttling provides a linear behaviour but it can only be applied to configurations with multiple combustion chambers. Finally, the effects of different plug truncation levels are discussed. Full article

The traditional valve-controlled hydraulic servo system has large throttling losses and undergoes serious heat problems when used in electro-hydraulic servo systems (EHSSs) for a rolling shear. In order to improve the energy efficiency of the EHSS for the rolling shear while also ensuring the position tracking accuracy, the separate metering electro-hydraulic servo system with varying supply pressure (VSP-SMEHSS) is proposed in this work. The inlet valve controls the position of a hydraulic cylinder, while the outlet valve controls the back pressure of the hydraulic cylinder. However, due to the disturbance caused by the varying supply pressure, the proportional–integral–derivative (PID) controller or active disturbance rejection controller (ADRC) cannot meet the requirements of accuracy. In order to solve this problem, based on a nonlinear disturbance observer (NDO) and a tracking differentiator (TD), a dynamic surface control (DSC) is proposed in this work. Firstly, the stability of the controller is validated using the Lyapunov method. Then, experiments are conducted to verify the proposed control strategy. As a result, the hydraulic cylinder can accurately track the reference displacement signal and effectively reduce the pressure drop at the valve’s orifice, due to which the hydraulic system achieves significant energy-savings. Compared with that of the EHSS, the energy consumption of the VSP-SMEHSS is reduced by 44.6%. Full article

Hydrostatic actuation has gained interest from both academia and industry due to the unquestionable energetic advantages when compared to valve-controlled actuators; the main feature being the absence of throttling losses due to the direct control of the cylinder by the pump. However, the fact that the great majority of applications are based on single-rod cylinders has been both a challenge and a source of inspiration for a variety of different circuit designs. In an attempt to compensate for the uneven flows coming in and out of differential cylinders, several solutions have been proposed, including the use of hydraulic transformers, individual pumps connected to the cylinder ports or pumps with unmatched input and output flows. The simplest approach, however, seems to be the use of compensation valves in the circuit, which is the focus of this paper. Here, we analyse some representative circuits proposed along the years in a direct and elucidative manner, showing that the definitive solution to the single-rod actuator control problem has been established, paving the road for introducing stable and trustworthy circuits, which can be commercially used in the near future. Full article